Low FPS on Animation Playback
Things you can try to improve viewport performance:


Enable VBOs in User Preferences > System. This should speed up drawing of highly complex scenes with lots of geometry.
Enable Only Render under the display panel of the 3D viewport. This will hide extra lines and wireframes, which are slow to draw.
Disable Double Sided in the object properties editor for high polygon mesh. This is especially helpful on Fermi-level Nvidia cards.
Turn off modifiers you don't need in the viewport.
Use Simplify in the Scene property editor to globally reduce the complexity of the scene.
Make sure you are viewing the scene in Solid mode, it's typically faster than all the other mode, including wireframe.
If you are using physics simulations like particles or cloth, make sure they are baked. Otherwise, Blender will try to recalculate them every time you switch frames.